Photochemical exploration method



Patented Aug. 4, 1942 PHOTOCHEMICAL EXPLORATION METHOD Robert 0. Smith,Fort Worth, Tex.

No Drawing. Application July 10, 1940,

Serial No. 344,736

, 8 Claims.

This invention relates to a method of geophysical prospecting for hiddenpetroleum deposits by the detection and subsequent correlation ofevidences of concentrations of petroleum derived constituents, such assaline products, and it has particular reference to a method embracingthe systematic collection of a series of samples of soil at or near theearth's surface along predetermined reconnaissance surveys, preservingthe said samples in containers impervious to air and moisture, andsubjecting the same to laboratory procedure calculated to disclose datawhich may be tabulated and subsequently correlated to produce adefinitely outlined area or closure within which the production ofpetroleum may reasonably be expected.

The primary object of the invention resides in the provision of a methodof geophysical exploration whereby the perimeter of an anomaly maybecome apparent at the earth's surface so that, whena map of the areaunder examination has been prepared, an outline of, or halo above theproductive area can be definitely fixed, enabling the operator todetermine where petroleum production is most likely to occur and toafford a reliable means of establishing a favorable drilling'location.

Among the petroleum derived constituents known to be indicators ofhidden petroleum deposits are saline products which are considered veryimportant and the present invention deals primarily with such indicatorsand particularly with alkaline salts (NaCl, KCl, etc.) which are knownto migrat to the earth's surface in varying quantities from subterraneanpetroliferous deposits and are found in definite concentrations atpoints at the surface above the edges of salt domes, and similarstructures.

It is of general knowledge that saline constituents of the soil are moreor less constant throughout theearths surface and random examinations ofsoil samples offer no assurance of the emanation of such derivativesfrom a petroliferous source,'but where samples are consistently taken atdefinitely spaced intervals over a certain area, and concentrations ofthe products appear evident from consistent correlation, it may well besup-- posed'that a petroleum bearing anomaly exists therebelow.

Leakage products from petroleum deposits also consist of several typesof hydrocarbons, primarily methane, and other gaseous products, which Ihave also considered as evidenced by my previous applications, as forexample Serial No.

280,431, filed June 22, 1939; Serial No. 298,449,

1 ably be expected.

While there are several methods of laboratory procedure I employ, Iprefer to place about two (2) grams of each sample in a container,preferably a tube of conventional size, and add enough pure distilledwater thereto to thoroughly immerse the soil. The tube is shaken oragitated sufficiently to cause the soil to be thoroughly suspended inthe water. The soil is then allowed to settle in the tube and until thealkaline salt (NaCl, KCl) content of the sample has been whollydissolved in water.

After suflicient agitation and settling ofthe soil sample has beenaccomplished to effect the thorough dissolution of the alkaline saltcontent of the sample in the water, the solution is posure is made, butall of the said samples must 7 be exposed for the same period of timefor and uniform results.

The length of the period of exposure depends largely upon the angle ofthe rays, if the sample is subjected to sunlight, since the rays earlyin the morning or late in the afternoon are projected at a more acuteangle and require longer exposure to obtain the proper results. A moreuniform period of exposure can be accomplished, of course, by theapplication of artificial rays, which is sometimes practicable anddesirable, in the absence of natural ultra-violet rays from the sun, butsuch application ,is not always conveniently accessible nor aseffective.

Atthe end of the exposure period, if all of the samples, each beingdeposited in separate tubes, have been uniformly exposed, the solutionswill appear in various hues and shades of yellow, orange, red, purpleand dark purple, as progressions from the original pure crystal clearwater to an almost black color, the latter reflecting the largestquantity of alkaline salts (NaCl) present colors reflect the greaterconcentrations of the product (NaCl) while the lighter hues andvariations of color reflect the lesser quantities of the product presentin the samples and are recorded accordingly on the chart. For example,the hues which manifest themselves during a predetermined period ofexposure, such as yellow, orange, red, purple, and dark purple, aregiven quantitative values according to their variation of density, basedupon parts per million, and are recorded along the ordinate of a chartwhile the sample stations are designated along the abscissa thereof andthe curve, commonly referred to as the mineral curve, interpretativelyrecords the results of the investigation, and the peaks and recessionsof the curve will enable the interpreter to outline the definiteproductive structure on the map of the area.

After an observation of. the general geological pattern of the area hasindicated a salt dome structure, a radial survey is made which consistsof several reconnaissance lines radiating from a common point, alongeach of which a se-' ries of samples are taken, properly identified bystation number and survey, and transmitted to the laboratory. A curve isthen made from the laboratory findings for each reconnaissance line, andthese several lines are afterwards correlated with each other toestablish the outline or perimeter of the closure under considerationand such closure is outlined upon the map of the area.

The curves, as stated, reflect pronounced peaks and recessions alongeach survey, the' peaks, when found to be more or less pronounced andconsistent, indicating the greater concentrations of the productssought, and thus clearly indicate the outline of the structure, whenproperly correlated with other surveys, so that the outlineor halo maybe readily depicted upon the map of the area.

A quantitative value may be arbitrarily adopted for each color or tint,according to the individual requirement, it being necessary only todetermine the points of greatest concentration of the product along thesurvey and to be able to accurately and definitely fix theseconcentrations upon correlation of the several surveys of the area. Onlya quantitative determination of the relative content of the productialkaline salts) of each soil sample taken over any given survey isnecessary to be considered and it is not required that an exactquantitative measurement of the product be had so long as the peaks andrecessions appearaing on the chart are sufficiently pronounced to enablethe interpreter to point with reasonable certainty to a definite outlineof the structure under examination.

The reaction of the alkaline salts products, when contacted by thesilver nitrate solution, strongly resembles the reaction which ismanifest in photochemistry and for this reason I prefer to refer to mymethod as a photochemical process. The procedure herein described may bemodified, particularly with respect to the length of time the varioussamples are exposed to ultraviolet rays, since the longer eachsample isexposed the darker the color it assumes, and continuous exposure wouldresult in coloring each sample a dark purple which, in appearance, wouldbe almost black. It is highly essential, therefore, that all of thesamples be exposed for a uniform period of time, regardless of theperiod of exposure decided upon. It has been stated that a period of ten(10) minutes is deemed to be a sufficient length of time to obtain thebest results. However, it is obvious that greater periods of exposuremay be adopted, if desired, with equally responsive results althougheach sample may be shades darker, necessitating the establishment of adifferent quantitative valuation for basic consideration.

In accomplishing other than radial surveys, heretofore referred to, suchstructures as faults, and the like, may be detected by laying out aseries of reconnaissance surveys in parallel relationship, which may bereferred to as a grid survey, so that when the resultant curve iscorrelated in each instance the excessive peaks thereof, indicating theconcentrations of the product, will point to a definite structure whichmay extend along a course simulating a fault, or other similarstructure, and coupled with surface geology may indicate a valuableanomally.

'Manifestly, the method herein described may be modified by personsskilled in geophysical and geochemical sciences in the course ofexperimental and practical application and such modifications as may beresorted to from time to time and which may be considered as fallingwithin the spirit and intent of the method as herein outlined may alsobe considered as falling within the scope of the appended claims.

What is claimed is:

1. In the art of geophysical exploration for hydrocarbon deposits, themethod of detecting concentrations of hydrocarbons over buried depositsby the determination of the saline products in the soil comprisingsystematically selectingsoil samples over the area, dissolving out thealkaline content of the said samples in pure water, adding a silvernitrate solution to the said alkaline solution, subjecting the mixtureto ultra-violet rays for a predetermined period and measuring thehydrocarbon content by resultant color and tint variations.

2. In the art of geochemical exploration for hydrocarbon deposits, themethod of determining the alkaline content of the soil overlyingsuspected petroleum deposits by systematically collecting soil samplesover a predetermined course, dissolving the alkaline salt content ofeach sample in pure water, adding a quantity of a silver nitratesolution to the said alkaline solution, subjecting the resultant mixtureto light rays for a predetermined period and establishing thehydrocarbon content of each sample by the resultant color and tintvariations. I

3. The method of locating hidden hydrocarbon deposits through thequantitative determination.

of alkaline properties of the soil overlying a suspected petroleumdeposit which consists in collecting samples of soil overlying the saiddeposits, immersing a quantity of each sample in pure water to dissolveout the alkaline salt content thereof, decanting the solution and addingthereto a quantity of silver nitrate solution, subjecting the mixture tolight'rays and measuring the hydrocarbon content of each sample by theresultant color and tint variations.

4. The herein described method of locating hidden hydrocarbon depositsby the determination of the alkaline contents of the soil thereoverwhich consists in selecting samples of the said soil systematically overthe area under investigation, dissolving the alkaline salts from eachsample in pure water, mixing a quantity of the centrations of alkalineproperties in the soil above the said depoflts at the surface whichconsists in selecting samples of soil at predetermined intervals along afixed course, dissolving the alkaline salt content from each sample inpure water, adding a solution of silver nitrate to the saidalkalinesaltsolution, subjecting the mixture from each sample to lightrays for a predetermined period, measuring the hydrocarbon contentof'each sample by the resultant color and tint variations and indicatingthe said measurements with respect to the original location of the saidsample.

6. In the art of exploration for petroleum deposits by geochemicalinvestigation to determine the alkaline contents oi the overlying soilwhich consists in sysmetlcally selecting a series oi. soil samples alonga predetermined course, dissolving the alkaline salts from each samplein pure water, decanting the solution, adding a quantity of a solution01' silver nitrate to the'alkaline salt solution from each sample,exposing the combination to ultra-violet rays for a predetermined periodand measuring the hydrocarbon content of each sample by the color andtint variations thereof resulting from said exposure.

7. In the art of geochemical exploration for hydrocarbon deposits in theearth, the method of detecting concentrations of surface hydrocarbonsindicated by the concentration of saline products of the soil above thesuspected deposits which consists in systematically selecting a seriesof soil samples over the area under consideration, dissolving thealkaline salts from each sample in pure water, adding a fixed quantityor a silvernitrate solution to the alkaline saltssolution from eachsample, subjecting the same to ultra-violet rays and measuring thehydrocarbon content of each sample by the resultant color and tintvariations.

8. In the art of exploration for buried hydrocarbon deposits bydetecting the surface hydrocarbon concentrations of the soil thereaboveindicated by the saline concentrations of the said soil consisting insystematically selecting a series of soil samples, immersing each of thesaid samples in pure water. to dissolve out the alkaline salt contentthereof, decanting the solution and adding thereto a quantity of asolutionv or silver nitrate, subjecting the mixture to ultra-violet raysfor a specified period and measuring the hydrocarbon content of eachsample by the resultant variations in color and tint thereof.

" ROBERT 0. SMITH.

